Non-thread safe singletons can result in bad state changes. Eliminate static singletons if possible by instantiating the object directly. Static singletons are usually not needed as only a single instance exists anyway. Other possible fixes are to synchronize the entire method or to use an initialize-on-demand holder class (do not use the double-check idiom). See Effective Java, item 48.

<p>
  This rule is deprecated, use {rule:squid:S2444} instead.
</p>
